Electrical fitting



June 24, 1941. L. HOPKINS ELECTRICAL FITTING Filed March 15, 1940INVENTQR 9 a 7 a 9 n? 1 M f H I {U m J a A M I m 8 4. 1 5 1/ 6 0 2 3 4 Lw NHNMM 2 l .1 2 A Ill m m M- E a VIM: \4 u (U1 6 3 Patented June 24,1941 ELECTRICAL FITTING Llewellyn Hopkins, Butler, Pa., assignor ofonehalf to John V. Cowden, Butler, Pa.

Application March 13, 1940, Serial No. v323,748

8 Claims.

My invention relates to electrical fittings, and more particularly tothose of the plug-in type,

wherein a plug having contact fingers is inserted into a receptacle orbase having slots for receiving the fingers, and fixed terminals arelocated at the inner ends of said slots, for electrical contact withsaid fingers.

In devices of this character, it frequently happens that there will besuch loose engagement between the conductor fingers and the terminalelements in the base that slight vibration or movement will causeinterruption of the electrical circuit. Again, a slight pull on thewires or cable to which the plug is connected maycause the plug to bewithdrawn from the base, or the receptacle may be mounted in a ceilingand the plug may fall out.

My device is of general utility and in addition to being desirable forhousehold and other general uses, it embodies a safety feature whichwill reduce hazards to employees in mills, one specific use being in thecase of cranes and magnetic lifting devices, where accidentalinterruption of electrical current may result in loads which are beinglifted and transported dropping upon workmen or machinery.

My invention has for its object the provision of an improved meanswhereby the electrical plug will be locked automatically and firmly inthe base or receptacle when the switch is closed.

In the accompanying drawing, Figure 1 is a side view showing the plug insection and also showing the base; Fig. 2 is a view showing certain ofthe parts of Fig. 1 removed from the casing; Fig. 3 is a perspectiveview showingcertain of the locking elements of Figs. 1 and 2,independently of the switch elements; Fig. 4 is a plan view of the baseof Fig. 1, and Fig.5 isa detail view of a portion of the structure ofFig. 3.

The apparatus comprises a base or receptacle 5 which may be ofconventional form in that it can be screwed into a socket that hasterminal or contact members with which the conductor elements '6 and lof the base will make electrical contact. The base is ako provided withslots or holes 8 and 9 for the reception of contact fingers carried bythe plug, so that the fingers will engage the usual conductors in thebase, for completing the circuit through the fingers and the elements 6and I. The parts thus far specifically referred to are of any well-knownconventional form. It will be understood that bases of other forms thanthat just described may be employed, if they have recesses or openings 8and 9 for the reception of contact fingers.

The plug may be of somewhat conventional form in general appearance, inthat it comprises an outer metallic case II] lined with insulatingmaterial II and provided with contact fingers or pron s I2 and I3 thatcan be inserted into the openings 8 and 9, and also being provided witha switch for completing a circuit from conductors I4 and I5 through thecontact members I2 and I '3. The switch is here shown as of the singlepole,

two-point break type and comprises a blade I6 that is pivotally mountedat I! upon one leg of a bracket I8 of inverted U-form, the switch bladebeing insulated at H from the bracket. Upper switch jaws are secured at28 to the bracket I8, but are insulated therefrom and have electricalconnection with the wire I4 by a terminal screw at 20. The lower switchjaws 2I are secured to the lower portion of the bracket I8 by a terminalscrew 22, the jaws and the screw being insulated from the bracket. Theprong I2 has electrical connection through the screw 22 with the jaws2i.

A switch lever 23 is pivotally connected at-ZII with the opposite leg ofthe bracket I8 and pivotally carries a link25 that has rigid connectionat 26 with an arm 21 that is pivotally connected with'the switch bladeI6, the arm being insulated from the link 25. The wire I 5 is connectedto the upper end of the finger I3, the said finger being secured to thebracket I8 by an insulated connection at 29. It will be seen that as theswitch lever 23 is moved up and down, the blade IE will be oscillated tomake and break the circuit through the wire I4 and the finger I2.

A screw-threaded ferrule 3I has threaded connection with a bushing 32which is secured in the upper end of the switch casing and extendsthrough a hole formed in the upper end of the bracket l8 and hasthreaded connection at 33 with a gripping device 34, which is shown indetail in Fig. 3. The gripping device has twopairs of jaws 35 and 36that are of spring-like material, the jaws being yieldably urged towardexpanded position by interposed coil springs 3'! and 38 respectively.

The link 25 carries at its lower end a pair of yokes Hand that embracethe jaws 35 and 36 respectively, so that when the switch lever is moveddownwardly to rock the switch blade I6 in a counter-clockwise directionto bridge the switch jaws I9 and 2|, the yokes 39 and 40 will also bemoved down to draw the jaws of each paid toward one another.

As indicated more clearly in Fig. 5, the yokes 39 and 40 haveantifriction rollers 43 journaled therein, to reduce friction with themembers 35 and 36, and the members 35 and 36 have recesses 44 formedtherein, so that the yokes will be yieldably held in their lowerpositions, and the switch blade I 6 consequently yieldably held closed.Also, the expansive force of the springs 31 and 38, when the yokes arein their upper position, will tend to hold the movable switch parts withthe blade in open positionagainst accidental closing.

When the plug has been placed in assembled relation with the base 5, andwith the fingers l2 and I3 in electrical contact with the conductorelements in the base 5, movement or" the switch lever 23 in a clockwisedirection about its pivot 24 will move the switch blade l6 into itsclosed-circuit position and will also move the yokes 39 and 40downwardly to draw the jaws together, so that the jaws will engagebeneath the'heads of anchoring studs 42 that are embedded in orotherwise rigidly connected with the base 5, so that the plug will beheld firmly in assembled relation with the base 5, thus insuring againstaccidental displacement therefrom or relative vibration. This anchoredconnection will be maintained so long as the switchremains closed.

I claim as my invention:

1. In an electrical fitting, the combination with a base and a plughaving conductor fingers insertible into the base, of a pair of headedretaining elements projecting outwardly from the base, hook memberscarried by the plug and each having one end connected to a fixed portionof the plug, and a slidable yoke-like member for effecting movement ofthe other ends of said hook members into hooked engagement with saidretaining members. 7

2. In an electrical fitting, the combination with a base and a plughaving conductor fingers insertible into the base, of a switch carriedby the plug, a retaining element on the base, a hook member having oneend connected to a fixed portion of the plug, and means operated throughcircuit-closing movement of the switch, for moving the other end'of thehook member into hooked engagement with said retaining element andrigiidly maintaining said member in such position.

3. In an electrical fitting, the combination with a base havingconductor elements arid a plug having conductor elements positioned toengage the first-named elements when the plug and the base are inassembled relation, of retaining shoulders on the base, hook memberscarried by the plug and each having one end connected to a fixed portionof the plug, and means for moving the other ends of the hook membersinto position behind the shoulders to effect interlocking en-,

gagement therewith and rigidly maintaining said members in suchposition.

4. In an electrical fitting, the combination with a base havingconductor elements and a plug having conductor elements positioned toengage the first-named elements when the plug and the base are inassembled relation, of retaining shoulders on the base, hook memberscarried by the plug and each having one end connected to a fixed portionof the plug, and a yoke movable to efiect lateral movement of the otherends of the hook members to and from interlocking position behind thesaid shoulders.

5. In an electrical fitting, the combination with a base havingconductor elements and a plug having conductor elements positioned toengage the first-named elements when the plug and the base are inassembled relation, of retaining shoulders on the base, hook memberscarried by a fixed portion of the plug, a yoke movable to efiect lateralmovement of the hook members to and from interlocking position behindthe said shoulders, and a lever pivotally mounted on the base, foroperating the yoke to move the hook members into position behind theshoulders to efi'ect interlocking engagement therewith.

6. In an electrical fitting, the combination with a base havingconductor elements and a plug having conductor elements positioned toengage the first-named elements when the plug and the base are inassembled relation, of retaining shoulders on the base, hook memberscarried by a fixed portion of the plug, a yoke movable to efl-ectlateral movement of the hook members to and from interlocking positionbehind the said shoulders, a lever pivotally mounted on the base, foroperating the yoke to move the hook members into position behind theshoulders to effect interlocking engagement therewith, a switch actuatedby said lever to open the switch when the lever is moved to release thehooks, and means for yieldably holding the lever in its open-switchposition.

'7. In an electrical fitting, the combination with a base havingconductor elements and a plug having conductor elements positioned toengage the first-named elements when the plug and the base are inassembled relation, of retaining shoulders on the base, hook memberscarried by a fixed portion of the plug, a yoke movable to efiect lat-,eral movement ojf the hook members to and from interlocking positionbehind the said shoulders, a lever pivotally mounted on the base, foroperating the yoke to'move the hook members into position behind theshoulders to efiect interlocking engagement therewith, and a switchoperated through movement of said lever, in a direction to close thecircuit, when the hook members are moved into said interlockingposition. 8. In an electricalfitting, the combination with a base havingconductor elements and a plug having conductor elements positioned toengage the first-named elements when the plug and the base are inassembled relation, of retaining shoulders on the base, hook memberscarried by a fixed portion of the plug, a yoke movable to effect lateralmovement of the hook members to and from interlocking position behindthe said shoulders, a lever pivotally mounted on the base, for operatingthe yoke to move the hook members into position behind the shoulders toeirect interlocking engagement therewith, a switch operated throughmovement of said lever, in a direction to close the circuit, when thehook members are moved into said interlocking position, and means foryieldably holding the switch in open position when the yoke is inposition to efi'ect release of the hook members from said shoulders.

LLEWELLYN HOPKINS.

